The present invention relates to a multi-piece solid golf ball composed of a core, a plurality of envelope layers, an intermediate layer and a cover that have been formed as successive layers. More specifically, the invention relates to a multi-piece solid golf ball which has a flight performance and controllability that satisfy the needs of professionals and other skilled golfers, and which also has a good feel on impact and an excellent scuff resistance.
A variety of golf balls have hitherto been developed for professionals and other skilled golfers. Of these, multi-piece solid golf balls having an optimized hardness relationship between an intermediate layer encasing the core and the cover layer are in wide use because they achieve both a superior distance in the high head speed range and good controllability on shots taken with an iron and on approach shots. Another important concern is the proper selection of thicknesses and hardnesses for the respective layers of the golf ball so as to optimize not only flight performance, but also both the feel of the ball when played as well as its spin rate after being struck with the club, particularly given the large influence these latter factors have on ball control. A further key concern in ball development, arising from the desire that golf balls also have durability under repeated impact and scuff resistance against burr formation on the surface of the ball when repeatedly played with different types of clubs, is how best to protect the ball from external factors.
The three-piece solid golf balls having an outer layer cover formed primarily of a thermoplastic polyurethane which are disclosed in, for example, JP-A 2003-190330, JP-A 2004-49913, JP-A 2004-97802 and JP-A 2005-319287 were intended to meet such needs. However, because these prior-art golf balls fail to achieve a sufficiently lower spin rate when hit with a driver, professionals and other skilled golfers have desired a ball which delivers an even longer distance.
Meanwhile, efforts to improve the flight and other performance characteristics of golf balls have led to the development of balls having a four-layer construction—i.e., a core enclosed by three intermediate or cover layers—that allows the ball construction to be varied among the several layers at the interior. Such golf balls have been disclosed in, for example, JP-A 9-248351, JP-A 10-127818, JP-A 10-127819, JP-A 10-295852, JP-A 10-328325, JP-A 10-328326, JP-A 10-328327, JP-A 10-328328 and JP-A 11-4916.
Yet, as golf balls for the skilled golfer, such balls provide a poor balance of distance and controllability or they fall short in terms of achieving a lower spin rate on shots with a driver, thus limiting the extent to which the total distance can be increased.
Multilayer golf balls having a core and a four-layer cover have been disclosed in, for example, JP-A 2001-17569, U.S. Pat. No. 6,416,425 and JP-A 2001-37914. Efforts have been made to improve overall the ball performance by optimizing such properties of these multilayer balls as their core deflection (deformation) and the hardnesses of the respective covers.
However, these latter multilayer golf balls too leave something to be desired as golf balls for the skilled golfer in terms of one or more of the following attributes: distance, controllability, feel on impact, durability to repeated impact, and scuff resistance.